The present invention relates to wiper blades for motor vehicle windows.
In wiper blades the carrying element should ensure that the pressure exerted by the wiper arm to press the wiper blade against the windshield is distributed as uniformly as possible over the entire wipe field wiped by the wiper blade. Due to a corresponding curvature of the carrying element when it is not loaded--that is, when the wiper blade does not rest against the windshield--the ends of the wiping strip which rests in its entirety against the windshield during operation of the wiper blade are loaded toward the windshield by the carrying element which is now tensioned, even though the radii of curvature of spherically curved vehicle windshields change in every position of the wiper blade. Therefore, the curvature of the wiper blade must be somewhat greater than the greatest curvature measured in the wipe field of the windshield to be wiped. The carrying element accordingly replaces the elaborate carrying clip construction by two spring rails which are arranged in the wiping strip as is conventional practice in wiper blades.
In a known wiper blade of this type (DE 26 14 457 A1), the stop surfaces are arranged at shoulders that are connected integral with the carrying element and that belong to the apparatus for connecting the wiper blade to the driven wiper arm. These shoulders are accordingly made from the same material as the carrying element. This may possibly be of secondary importance provided that the carrying element is made from plastic and is therefore manufactured, along with the shoulders, by filling an appropriate mold. However, if the carrying element is produced from metal, there are two diametrically opposed requirements. Namely, on the one hand, the carrying element should have good spring characteristics, but the shoulders, on the other hand, should be easily bent out of the plane of the carrying element by approximately 90 degrees and fixed in this position so that the loading occurring during operation between the wiper blade and wiper arm can be absorbed at the stop surfaces. These two requirements can scarcely be met in practice without disadvantageous compromises with respect to the selection of material.
In another known wiper blade (DE 12 47 161), the carrying element is provided with a connection device formed as a separate structural component part. This connection device is fixedly connected with the carrying element by means of rivets. However, the bore holes which are required in the carrying element for this purpose, the rivets being seated therein so as to be mechanically clamped, lead to an uncontrollable, and hence unwanted, change in the tensioning of the carrying element, so that satisfactory wiping results cannot be achieved.